Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)
It’s 9:30 a.m. EDT, which is 10:30 p.m. on Friday evening in Japan. [Updates below.]
[Update II, 11:00 a.m. EDT]: Kyodo News reports workers have begun to inject fresh water into the reactors at Units 1 and 3 (Unit 2 is next) to help flush sea water and salt buildup out of the reactor and cooling water systems. That’s a good step, because salt buildup can lock the valves and inhibit water flows within the reactor. (They’re still spraying sea water into the spent fuel storage pools.) They’re also finding more radioactive water leaks and standing water in other units. ]
Concerns on Friday focused on (1) the continuing spread of radiation in Fukushima and surrounding prefectures, with local citizens anxious to evacuate areas beyond the mandated 20 kilometer radius and (2) the inability of the government either to gain control of the crippled Fukushima Daiichi reactors or to explain the exact source and nature of the continuing radiation leaks.
The latter concern increased yesterday when authorities reported that three workers suffered radiation exposure while standing in water, trying to lay cables to connect an outside electrical power cable to Unit 3. (Power cables are already connected at Units 1 and 2; see previous updates.)
Two of those workers had to be hospitalized for possible radiation burns on their feet. [A late medical report claims that two of the three exposed workers do not appear to have skin damage but have suffered from "internal exposure."] Initial reports jumped at the claim that the workers had walked through puddled water (with no protective boots) outside the reactor building and that the exposure levels were “10,000 times normal exposure levels.”
Since normal levels are extremely small, the “10,000 times normal” figure was not the only point. Rather, the concern quickly shifted to where the exposure occurred, where the water was coming from and how it became contaminated. I originally thought the source might be runoff from the sea water spraying, but that assumed the water was outside. It was inside.
It now appears the workers were inside a part of the turbine/generator building, which is separate from but connected to the reactor building. The connections with the reactor include a series of pipes that carry pressurized steam from the reactor to the turbines, which then drives the generators to produce electricity. Other pipes then carry the cooler condensed water back to the reactor. There are various valves along the way.
[Update I]: as the NYT reports, there are pipes from the reactor carrying away corrosive materials from the reactor to a filtering system inside the turbine-generator building.
But Michael Friedlander, a former nuclear power plant operator for 13 years in the United States, said that the presence of radioactive cobalt and molybdenum in water samples taken from the basement of the turbine building of reactor No. 3 raised the possibility of a very different leak.
Both materials typically occur not because of fission but because of routine corrosion in a reactor and its associated piping over the course of many years of use, he said.
These materials are continuously removed from the reactor’s water system as it circulates through a piece of equipment called a condensate polisher, which is located outside the reactor vessel. The discovery of both materials in the basement suggests damage to that equipment or its associated piping, as opposed to a breach of the reactor vessel itself, Mr. Friedlander said.]
Did the excess irradiated water on the floor of the turbine/generator building come from leaks in these pipes or valves coming from/returning to the reactor building? That would indicate the source of the irradiated water was inside the reactor itself, not the spent fuel storage pool. And the type of irradiation would be another sign, if they needed one, of likely breakdown, possibly continuing, of fuel inside the reactor core [or corrosion in the reactor]. But as of Friday night, they apparently had not found the “leak” inside the turbine/generator building, so they’re haven’t confirmed this scenario.
Regarding the other units, a Defense Forces helicopter made an overhead video of the four reactor buildings. It’s shown periodically on the NHK TV feed and gives a better perspective on the damage to each reactor.
At Unit 1, where a hydrogn explosion a week ago destroyed the upper walls and roof of the reactor, we can now see that the roof was not blown off; it collapsed down, effectively covering the reactor components and spent fuel storage pool below. Commentators explaining the video did not know how much that complicates the ability to spray water into the storage pool from above, so it’s not clear how they’re maintaining cooling water levels in the storage pool.
At Unit 2, the earlier hydrogen explosion caused minimal damage to the exterior of the reactor building, but it is suspected of causing damage at least to the pressure suppression pool at the bottom of the reactor. In an emergency, if pressure builds up inside the reactor, it can inject steam into the suppression pools to relieve the pressure and cool the reactor down, while cooler water is, one hopes, injected back in. We so much damage from the top, we can’t see that lower structure in this video. The emergency crews punched out two holes in the building exterior, one in the upper levels on one side, another in the roof. They did this to allow venting of steam to prevent another hydrogen explosion, and you can see steam escaping from both holes.
At Units 3 and 4, explosions at each caused massive damage to the external building and likely serious damage to some components inside. For example, among the twisted steel rubble at Unit 4, you can make out a green structure that might have been the massive crane that operates above the reactor vessel and that is used for moving fuel rods in and out of the building and between the reactor vessel and the spent fuel storage pool. If that fallen structure we see is the crane, the question is, what did it damage on the way down? It’s usually above the reactor vessel, the containment structure, the spent fuel storage fuel and lots of critical coolding/steam pipes and valves, etc.
The inability of authorities to get these events under control, and continuing reports of worker exposure, unsafe tap water and produce is naturally increasing the alarm among residents. TV interviews are showing more and more folks saying they want to leave, just get out, but not getting answers they believe from the Japanese Government. Government officials are now saying it’s okay for folks within the 30 kilometer radius to leave voluntarily, but as of Friday, they hadn’t ordered that evacuation. Instead, the Times reports they are quietly encouraging folks to move away. And it’s all complicated by the fact the quakes and tsunami left tens of thousands homeless and requiring massive relief efforts on water, food, shelter medical care.
They need a break, some good news, if the gods are listening.
Helpful Sources:
Kyodo News: Japan Nuclear Crisis
Picture of Unit 1 control room, via Kyodo News
Nuclear Power Plant Primer — good expert video
You can also find Unit by Unit status updates (pdf) at the IAEA site
